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Computer network model finds Parkinson’s tipping point

By Mark Buchanan

TOO much of a good thing can be bad for you. The synchronous firing of neurons is crucial for many ordinary brain functions, but excessive, uncontrolled synchronisation might be behind the symptoms of Parkinson’s disease. Now a computer model has backed up the idea.

Parkinson’s disease has been linked to a lack of dopamine, a chemical that, among other things, dampens the transmission of signals across nerve junctions called synapses. Measuring this effect in humans is not currently possible, so Leonid Rubchinsky and colleagues at Indiana University-Purdue University Indianapolis turned instead to a computer model of neural networks.

As they boosted signal strength, the network became more prone to switching from non-synchronised to synchronised firing. By comparing the pattern of neural signals recorded from people with Parkinson’s against those predicted by the model, the team found that in Parkinson’s, the brain readily switches between synchronised and non-synchronised behaviour even when it is relaxed. This might explain the disease’s motor symptoms.

A healthy brain fires synchronously in a brief and controlled way to coordinate motor behaviour and perform tasks. The stronger connections in the brains of people with Parkinson’s mean that attempts to coordinate behaviour trigger sustained synchrony, which may make it difficult to end a task or begin a new one (Physical Review E, in press).

“This is a simple and elegant study,” says Peter Brown of the University of Oxford. “The model beautifully captures the dynamic behaviour of the system.”